The Hayward Fault is an offset of the San Andreas Fault system that dominates the landforms of eastern San Francisco Bay.  The relative motion between the North American Plate  (southeast) and the Pacific Plate  (northwest) create stress that releases energy as earthquakes. This slip slide motion is called a transform fault.  The Hayward Fault is within the San Andreas Fault  Boundary Zone between the North American Plate and the Pacific Plate.  The Hayward fault is one of only a few dozen faults in the world that “creeps,” or slowly moves.  Evidence of creep can be found from Pt. Pinole in the north to south Fremont.

On the surface the Hayward Fault  is a right lateral strike-slip fault. A strike-slip fault is a vertical or near vertical break on the Earth’s surface where the ground moves horizontal in opposite directions. If you stand on the fault and the motion moves your right, it is called a right lateral. When an area of a fault moves suddenly it is called an “earthquake”.

The Hayward Fault  trends along the east side of San Francisco Bay. Traces of the Hayward Fault has been confirmed to be under San Pablo Bay and research indicates that the Rogers Creek Fault and the Hayward may be one continuous fault.  As you go south it runs from just west of Pinole Point on the south shore of San Pablo Bay and through Berkeley (just under the western rim of the University of California’s football stadium). The Berkeley Hills were formed by an upward movement along the fault. In Oakland the Hayward Fault follows Highway 580 and includes Lake Temescal. North of Fremont’s Niles District, the fault runs along the base of the hills that rise abruptly from the valley floor. In Fremont the fault runs within a wide fault zone. 

Around Tule Ponds at Tyson Lagoon the fault splits into two traces and continues in a downwarped area and turns back into one trace south of Stivers Lagoon.  When a fault takes a “side step” it creates pull-apart   depressions and compression ridges which can be seen in this area.  Southward, the fault lies between the lowest, most westerly ridge of the Diablo Range and the main mountain ridge to the east.   Coyote reservoir, Leroy Anderson reservoir, and San Felipe Lake all lie on the fault. It breaks from the San Andreas Fault near Hollister.

The Hayward Fault is slowly ripping  the City of Fremont.  The faulting is what has given this city its dramatic hills, and valleys making it a scenic and unique place.  Leland Stanford had his summer home in the Warm Springs area because of its hot springs caused by faulting.  His guests would bath in the springs in front of his summer mansion.   John Rock expanded the California Nursery Company in Niles, in a unique microclimate where the Hayward Fault changes from mountain to valley.  Lake Elizabeth, a human made structure prevents flooding downstream, and expands the large sag pond  caused by the down warping of the Hayward  Fault in this area.  Even the famous fossils beds in the Irvington District were exposed by the constant uplifting of one side that reveals a large river that would trap bones of large Ice Age mammals like mammoths and sabertooth cats.

In the picture below the trace of the Hayward Fault through Central Park is delineated in red.  The green circles represent evidence of creep or slow movement in a slip slide motion (transform).  The “Faulted Floor Exhibit” is just above Mission View Drive at Paseo Padre.   This map is based on scientific data obtained by Dr.  James Lienkaemper from the U.S. Geological Survey, Menlo Park. 

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